Texas_Ace BLF Calibrated Lumen tube / Sphere No math skills needed - Several spheres still available

Quick update, the soldering station is on it’s way, it should show up tomorrow or the next day it looks like since the holiday delayed it.

I have all the lights waiting here for mods, I will try to knock them out as quick as possible once it shows up. Sorry about the delay.

I have been quite the last few days as I am trying to catch up on some other real life items during the down time.

I'm now the owner of an HDS Systems Executive (200 lumens tested) and a modified Convoy S2+ from PFlexPRO (607 lumens, tested).

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THE HDS Systems Executive did not come with a calibration report, only a receipt stating it was 200 lumens (in addition to their website stating all lights are tested).

The PFlexPRO came with a calibration report (gotta love the potting sample in lower right):

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Unfortunately, the results of testing both on the TA lumens tube resulted in readings that don't make sense.

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HDS Systems

spec 200

TA Tube: 349

correction factor of .573

Note, I had an email discussion with HDS Systems (Henry Schneiker) to make sure initial turn-on (high) is where he measures the output. It was.

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Convoy S2+ (PFlexPRO)

spec 607 @ 30sec

TA Tube: 790

correction factor .768 @ 30sec

.573 and .768 is a BIG discrepancy. I was hoping to see both lights give results that were very close. The Convoy seems closer to what I expected.

I'm stumped.

The only other light that comes really close to the PFlexPRO correction factor would be my modified Maglite. Mat claims the 5,000 lumens is out-the-front.

What batteries and voltage did you use?

And this is the problem that I and many others have had with DIY spheres. You can get 10 flashlights all rated to given numbers but get very different relative readings. This is why I gave up on using flashlights for calibration.

What tints are the lights?

HDS has an ANSI calibrated sphere but they do not take the readings at the ANSI 30 second mark? That seems odd.

PFlexPRO says his sphere is calibrated with flashlights IIRC.

This is why all DIY spheres have to average the data from as many sources as possible to try to find a common middle ground that is semi-accurate.

This is also why I will never understand why anyone lists the lumen value on a light down to the single digits, they simply can’t know that.

I honestly don’t know what to think, I thought the calibration I had was pretty good when I started this as do many others but it seems a lot of us are wrong.

For the HDS Systems, I used the battery shipped with it - an AW 18650 (4.13V)

For the Convoy, I used a freshly charged Samsung INR18650-25R (4.10V)

I’m just waiting for you get your test lights back from Maukka, that he measured against his proper reference light, then test them across your remaining spheres to find the proper correction factor. That will probably be good enough for me. :+1:

I think it’s just human nature for us to want to see high lumen numbers from our lights. It’s hard to accept that a light that we thought was doing 9000 luman may actually be doing closer to 6000 lumen. Nooo! Say it ain’t true! Lol

It’s like we’re living in The Matrix and we’re starting to emerge from our pods and seeing the real world for the first time. Lol

Matt’s homemade integrating sphere was based on TA’s calibration if I recall correctly. So we shouldn’t go by that.

If PFlexPRO is not using a NIST calibrated reference light, then we should probably ignore those results as well.

HDS Systems uses turn on lumens? How odd. I wonder if he just verifies it meets the minimum 200 lumen specification? If so, then it could actually be more than 200 lumens.

Indeed, the only reason I trust Maukka’s numbers more then most is that he has an expensive standard lamp to compare against. This is the single most important factor to a quality sphere.

I am very curious to see what the numbers work out to. Some early data says it should agree with what most others are seeing in the high .6x range.

This is probably what they’re actual numbers are showing. It doesn’t mean it’s super exact. So you have to take it with a grain of salt. If it says 842 lumens then you know it’s probably 840 ish. Maybe even think of it as the mid 800 range.

Don’t beat yourself up about this. It’s not that big a deal.

Yeah, I know that and it doesn’t bother me directly so much as what the novice members among us think when they see those numbers. It propagates a false impression of exactness that we simply don’t have the capability of achieving.

For me the biggest attraction to your sphere project is the fact that a group of people here will have a standard to compare with each other - not some exact number.

Getting a lumen number is complicated… everyone
get different reading and different output…

I just realized that you don’t need to test the “Maukka measured” lights across your several tubes to find an average. Since those are all based off your original tube (plus or minus 5%) it means the original tube is the average. Duh, why didn’t I realize earlier. :person_facepalming: lol

To be fair, my standard lamp isn’t expensive. It’s just calibrated against one.

Sphere images.

No two identical flashlights ever give the same exact reading for a single integrating sphere as well. Cree bins their emitters plus or minus 7%, plus you have other smaller factors. :partying_face:

Maukka, since your test lamp sits in the middle of your sphere, how does its output compare to having it shining in through a port with a white background around it similar to how you would measure a flashlight shining into a port?

I guess it’s not very relevant for our purposes, but I was just curious.

Also, what did your standard light cost?

Does it also need a costly power supply to operate it?

The standard calibration light was under $100. The power supply doesn’t need to be super accurate as long as you have an accurate multimeter to verify the current stated on the calibration certificate when calibrating.

I used the calibration lamp inside the sphere in a E27 holder. After that I put the Emisar D4 in there at 100% 7135 for flashlight calibration (subtracting the effect of the D4 itself using an auxiliary light). After that I moved the D4 outside the sphere and measured the lux through a diffuser on the input port. I’ve noticed that a diffuser is the best single thing to improve the integration.

Now I had a calibration light for measuring other lights. I also measured the Haikelite SC02 as a second calibration light because its readings are very stable. Every time I measure lumens, I first check that the two calibration lights produce a calibration factor within 0.5% of each other. So I know if either of them has drifted for some reason.

For measuring lights I use an auxiliary light again to subtract their effect on the readings. With the diffuser in place, the small (<30mm) lights don’t really affect the readings, but for bigger lights the effect is clear (bigger readings when the reflector bounces light back to the sphere).

Great info and also glad to hear that I am on the right track with the diffusers, I noticed the exact same results when I added them to my sphere.

I finally was able to get caught up with all the flashlight mods, I have some other things to get caught up on over the next few days but I hope to start playing with ways to make a correction factor for the spheres after that. Hopefully the lights from Maukka will be here by then.

Has anyone tried sixty645’s method for calibration?

I have not tried that method exactly but I did try calculating the lumens early on in my sphere development and quickly dismissed it as the spheres we use are not nearly precise enough to mathematically calculate the lumens.

With a very high end “perfect” sphere, it should be possible though.